Method for preparing straight chain hexitol fatty esters



Aug. 22, 1961 w. F. HUBER 2,997,493

METHOD FOR PREPARING STRAIGHT CHAIN HEXITOL. FATTY ESTERS Filed Sept.29, 1959 nited tates Patent`v Y 2,997,493 METHOD FOR PREPARING STRAIGHTCHAIN HEXITOL FATTY ESTERS Wilson F. Huber, State College, Pa., assignorto The Procter & Gamble Company, Cincinnati, Ohio, 'a corporation ofOhio Filed Sept. 29, 1959, Ser. No. 343,178 18 Claims. (Cl. 260-410.6)

This invention relates to a process for preparing fatty esters ofpolyhydric alcohols.

More specifically, this invention relates to the preparaF tion ofpartial and complete -fatty esters of polyhydric alcohols having sixcarbon atoms in linear molecular configuration, such as sorbitol andmannitol.

As a matter of convenience, the following discussion for the most parttreats with sorbitol and mannitol and the derivatives thereof. It is tobe understood, however, that the discussion is equally applicable in thecase of all of the polyhydric alcohols (straight-chain hexitols)contemplated herein.

Many methods of preparing fatty esters of polyhydric alcohols are knownand have been heretofore employed. Among these are: The directesterilication of the polyihydric alcohols with fatty acids; reaction ofthe polyhydric alcohols 4with Afatty Aacid anhydrides; and the reactionof polyhydric alcohols with the fatty acid halides. Variousdisadvantages are identified with these previous processes, such asdifficulties in separating the desired products fro-m the reactionmixture, excessive temperatures necessary to promote the reaction withthe attendant adverse effects upon the organic reactants, includingthermal decomposition, charring, discoloration and the like. Mostparticularly, such processes promote the dehydration of the polyhydricalcohol molecule to the anhydro or inner ether form.

The prior Iart identities the products produced in accordance with theaforementioned process as, for example, sorbitol and mannitol esters.However, the products of these processes are not in fact the truesorbitol orV mannitol esters but are more correctly identified assonbitan and mannitan esters, the an ending indicating the presence ofthe anhydro conliguration in the ester molecule.

The partial fatty esters of the hexitols, the preparation of which iscontemplated in this application, are readily applicable whereemulsicat-ion problems require solution. For example, these esters maybe utilized in insecticides, textiles and industrial emulsions,dry-cleaning products and as constituents in detergent compositions.These esters are particularly applicable as emulsiiiers in thepreparation and formulation of various cosmetic and edible products,e.g. plastic shortenings, because of their non-toxic character. Forexample, they may be used in the preparation of cakes, candy, chewinggum, licorice, peanut butter, various beverages, pharmaceutical productsand vitamin oils. They may also serve as crystallization modifiers orinhibitors in salad oils. Although the sorbitanand mannitan-type esters,i.e. those esters containing anhydro groups, very probably havesatisfactory emulsification powers, such esters, identified as they arewith surface active agents, have not received Food and DrugAdministration approval for use with edible productsthe additive effectof a multiplicity of such agents which find their way into food productscreating serious doubt that they are suitable for such use. (See 17 Fed.Register 4453, No. 97 and Fed. Register March 26, 195 8, page 2007.)Consequently, the preparation of partial esters of straight-chainhexitols having substantially no anhydro groups present in the moleculeis of considerable commercial significance. However, the formation ofthe true partial esters of sorbitol and mannitol, i.e., those esterscontaining no anhydro groups, has been accomplished prior to the presentinvention, only through the process described and claimed in theco-pending application of lames B. Martin, Serial No. 793,820, entitled`Method for Preparing Fatty Esters, tiled February 17, 1959, or throughthe use of cumbersome and commercially impractical methods.

Although the prime consideration of this invention is the provision of amethod for preparing partial fatty esters of straight-chain hexitolswhich are substantially free of anhydro groups, it is to be appreciatedthat the process disclosed and claimed herein can also be utilizedY forpreparing ycomplete fatty esters of the hexitols.

With the foregoing considerations in mind, -it is an object of thepresent invention to provide a method' whereby fatty esters ofstraight-chain hexitols can be prepared under reaction conditions whichwill not promote the formation of anhydro configurations in the estermolecule.

A further object of this invention is to provide a process for thepreparation of fatty esters of straight chain hexitols substantiallyfree Ifrom molecular anhydro configurations which is commerciallypractical.

Other objects Iand advantages will be apparent fromthe followingdetailed descriptions taken in connection with the accompanying drawingin which single FIGURE I is a graph showing substantial conformitybetween calculated and observed values for products obtained byA thepractice of the invention.

It has lbeen found that the foregoing objects can be:

accomplis-hed by subjecting to interesterication a mixture of astraight-chain yheXitol and a fatty acid ester of an aliphatic primarymonohydroxy alcohol or a completelyA or incompletely estered fatty acidester of a polyhydricl alcohol having from 2 to 6 hydroxyl groups in thepre sence of a solvent selected from the group consisting of4 (l)sulfoxides of the general formula:

where R and R' are alkyl groups having from l to 3` carbon atoms and (2)amides of the general formula:

/Rl R-CON RII Where R and R are selected from the group consisting of,

hydrogen and an alkyl group having from l to 4 carbony atoms and R" isan alkyl group having from l to 4 carbon atoms, the total number ofcarbon atoms in R, R and R" being not greater than 7.

Generally speaking, the invention contemplates react-- ing thestraight-chain hexitol with the fatty acid ester inV the presence of analkaline catalyst which shows activity in interesterication reactions ata temperature in the range from about 50 C. to about 150 C. and in thev4presence of a solvent as described hereinbefore. Follow-t ing completion`of the interesterication of the compo-1 nents to the desired degree,the catalyst is inactivated by:

the addition of water and/or acids such as acetic, phos phoric, citric,hydrochloric and the like, and the desiredV reaction products are freedof solvent and puried by anyt suitable means.

The term straight-chain hexitol as used herein refers,l

Patented Aug. 22, 196i when yan amide-type solvent is used as thereaction medium, are the fatty acid esters of primary aliphaticmonohydroxy alcohols having from 1 to about 16 carbon atoms, forexample, methanol, ethanol, hexanol, octanol, dodecanol, andhexadecanol, specific examples being methyly palmitate, dodecylpalmitate and hexadecyl palmitate. When, however, a sulfoxide-typesolvent is used asthe reaction medium only the esters of aliphaticprimary monohydroxy alcohols containing from 1 to about 8 carbon atomscan be utilized as the fatty reactants.

In addition, fatty acid esters of completely or incompletely esterifiedpolyhydric alcohols, having from 2 to 6 hydroxyl groups such as glycol,glycerol, erythritol and pentaerythritol can be employed. Glycoldipalmitate, glycerol mono'-, diand tri-palmitate, erythritoltetrapalmitate and pentaerythritol tetrapalrnitate are examples of suchfatty esters. The use of fatty esters of the straightchain hexitols isalso contemplated. For example, the reaction of sorbitol hexapalrnitatewith sorbitol can be carried out in accordance with the presentinvention in order to obtain partial fatty acid esters of sorbitol.

The length of the fatty acid chain of the esters which can be employedin the reaction of this invention is not critical and is dictatedprimarily by the type of fatty acid material source available. As ageneral proposition, however, it has been found that fatty acidscontaining from about 8 to about 22 carbon atoms in the alkyl chain aremost useful. Therefore, the mixtures of fatty acids obtained fromanimal, vegetable and marine oils and fats, such as coconut oil,cottonseed oil, soybean oil, tallow, lard, herring oil, sardine oil andthe like represent readily availabIe sources of fatty acid radicals. Inthe event it is desired to produce straight-chain hexitol esters ofsingle fatty acids by this invention, then the individual fatty acidesters of the relatively volatile alcohols (e.g. methanol and ethanol),having from about 12 to about 22 carbon atoms in the fatty acyl chaincan be advantageously reacted with the polyhydric alcohol with theaidofV the particular reaction media herein disclosed.

Of the fatty acid esters which can be used in the practice `of thisinvention the esters of those alcohols having not more than 3 carbonatoms are preferred. In this group the fatty glycerides are particularlyadvantageous.

The choice of solvent is essential to the realization of theinteresterification of the straight-chain hexitol and the fatty esterunder the conditions hereinbefore set forth. It has been found thatsulfoxides and amides responding to the foregoing definitions areeminently suitable as solvent reaction media in the present process.

The proportion of solvent whichV is used as the reaction medium is notcritical and the reaction is successfully carried out so long as thereis suicient solvent present to dissolve the straightchain hexitols.Normally, the amount of solvent can be varied fro-m 0.2 to 50 times byweight of the straight-chain hexitol which is employedV fatty ester, theproportion of these reactants can bel chosen so that from one toessentially all of the hydrogen atoms of the hydroxyl groups of thesorbitol can be replaced by fatty acyl/radicals. Or, where sorbitol anda triglyceride are being reacted, proportions can be chosen so that thefinal product may predominate in either glycerides or in sorbitolesters. As a practical matter, however, it has been found that molarratios of straight-chain hexitol to fatty esters in the range from about3:1 to 1:6 are most satisfactory, the proportions of the reactants beingvariable within the range depending upon the co-mpleteness ofreplacement desired and upon the number of fatty acid radicals in eachmole of ester substance.

Although the process of the invention is illustrated herein with the useof sodium methoxide as the catalyst, effective practice of the processis not dependent upon the use of any particular catalyst. Rather, anyalkaline molecular rearrangement or interesterication catalyst whichwill promote the interchange of radicals among the reactants of theprocess is suitable. usable catalysts are: sodium methoxide, sodiumhydroxide, metallic sodium, sodium potassium alloy and quaternaryammonium bases such as trimeth-yl benzyl ammoniurn hydroxide. Adiscussion of other catalysts which are active in interestericatonreactions may be found in U.S. Letters Patent 2,442,532 to E. W. VEckey,column 24, line 18 et seq.

The sodium methoxide catalyst may be advantageously used in the presentinvention in amounts from aboutY 0.1 to about 2.0% by weight of thefatty ester which is to be reacted with the straight-chain hexitol.Equivalent amounts of other catalysts are, of course, also usable. Thechoice of catalyst and the amount which is to be used are dependent uponthe particular constituents which are to be reacted.

In the practice of this invention, it was observed that the reactionrate for a given solvent usage and a givenV catalyst increased with anincrease in temperature. With optimum amounts of solvent and sodiummethoxide as thek catalyst at a temperature of about 100 C. it was foundthat equilibrium was reached in about 1 to5 minutes time. Where lowertemperatures, suchY as 50 C., are employed a longer time is necessary toachieve desired ester formation. Temperatures abo've 100 C. and up toabout 150 C. can be employed as desired. Generally speaking, with any ofthe foregoing reactants or catalysts and Within the ranges ofproportions set forth the process of the invention is preferably carriedout at temperatures in the range from about 90 C. to' 115 C.

Although the process of this invention is normally carried out atatmospheric pressure it can be carried out at reduced pressure, anoperation which at times is decidedly advantageous. For example, when afatty acid ester of methanol is reacted with sorbitol in a processemploying dimethylacetamide or dimethylsulfoxide as the solvent reactionmedium, operation under reduced pressure such as about 100 to 300 mm. ofmercury enables the methanol formed as a result of theinteresteriication to be removed from the reaction zone substantiallyfasrapidly as it is liberated. This promotes a substantiallyr completeconversion of the methyl ester to Ysoribtol fatty ester.

Under the foregoing conditions it has been found that theinteresterication reaction may reach equilibrium in from about as littleas l0 up to about 90 minutes, the reaction being accelerated by anincrease in the amount of catalyst used or an increase in temperature.No adverse effects have been noted if the reactants are allowed toremain in contact under interesterication conditions Y- for considerablelengths of time, e.g. several hours, after the interestericationreaction is substantially complete. From a practical standpoint,however, little advantage is gained from such practice.

Since the reaction of the present invention is an interesterication inwhich sorbitol, for example, is reacted with a fatty ester, theresulting product of the reaction will constitute an equilibrium mixtureof sorbitol, esters thereof, displaced alcoholic substance from theester originally employed, and ester of such alcoholic substance. Thus,if triglycerides are reacted with the sorbitol then the product of thereaction will contain monoand diglycerides as well as sorbitol esters.If it is desired to obtain soribtol esters which are not so contaminatedwith originalesters and derivatives thereof, then it is preferable toreact volatile alcohol esters such as methyl or ethyl esters with thesorbitol and to conduct the reaction under reduced pressure so thatdisplaced alcohol is distilled off. Yields of sorbitol esters of highpurity Examples of v essaies.

ie obtainable in this Way since unre'acted volatile esters can beseparated subsequently by distillation or crystallization procedures.

'Ihe following examples will illustrate the manner in which theinvention can be practiced but it is to be understood that the specicconditions set forth in these examples are not to be considered limitingof the invention which is defined only by the scope of the appendedclaims. In the examples all parts are expressed by weight.

Example l 18 parts of mannitol, 162 parts of methyl palmitate and about180 parts of dimethylacetamide were introduced into a reaction vesselprovided with mechanical stirring means. This mixture was heated toabout 100 C. and then a suspension of sodium methoxide catalyst inxylene was added to the heated mixture in an amount equal to about 10%by weight of the methyl palmitate. The resulting mixture was allowed toreact, with agitation, for 1/2 hour at 100 C. and at atmosphericpressure. The catalyst was then inactivated by the addition of about 10parts of a 50% aqueous solution of acetic acid.

The reaction product was taken up in a 1:4 mixture of butanol and ethylacetate and was Water-Washed three times With hot Water. Thebutanol-ethyl acetate mixture was then removed from the product byevaporation under vacuum and the residue was steam deodorized at atemperature of from 130 to 150 C. and at a pressure of 1 mm. of mercuryfor one hour.

The ester product was found, upon analysis, to have a total fatty acidcontent of 75.8% and a hydroxyl Value of 387.2. This product can beeffectively used as an adjuvant in plastic shortenings wherein itsemulsifying properties promote improved performance of the plasticshortening in the preparation of baked goods.

Example II The process of Example I was repeated except that 54 parts ofmethyl palmitate was reacted with 18 parts of mannitol and thatdimethylsulfoxide was utilized as the solvent reaction medium in thesame amount as the dimethylacetamide solvent of Example I.

The ester product from this reaction -was found to have a hydroxyl valueof 247.4 and a total fatty acid content of 80.65%.

Example III 18 parts of sorbitol, 27 parts of methyl palmitate and about200 parts of dirnethylacetamide were introduced into a reaction vesselprovided with mechanical stirring means. This mixture was heated toabout 150 C. and then a suspension of about 9% sodium methoxide catalystin xylene was added to the heated mixture in an amount equal to about 1%by weight of the methyl palmitate. 'Ihe resulting mixture was reactedfor one hour at 150 C. under a pressure of about 600 mm. of mercury. Areduced pressure was utilized so that a portion of the methanol, formedas a by-product of the reaction, could be continuously removed from thereaction mixture. After the one hours reaction time the catalyst wasinactivated by the addition of a 50% aqueous solution of acetic acid.

The reaction product was then taken up in a 1:4 mixture of butanol andethyl acetate and was water-Washed four times after which thebutanolzethyl acetate mixture was removed from the product byevaporation under vacuum. The resultant product was crystallized fromabout 20 parts of a 1:1 mixture of dioxane and ethyl ether at 10 C. andvacuum dried for 18 hours at 70 to 80 C.

The ester product Was found, by analysis, to have a hydroxyl value of564.4 and a total fatty acid content of about 165.8%. The analyticallyobtained hydroxyl value value of 575 for the product, indicating thesubstantially complete absence of anhydro groups in the product..u

If desired, methyl laurate, propyl stearate, butyl oleate, hexylpalmitate, etc., can be substituted for methyl palmitate in thepreceding example to give a straight-chain hexitol ester withsubstantially the same degree of esteriiication and freedom from anhydrogroups.

Example IV The process of Example III was repeated exceptv that thereaction was conducted at a temperature of C. and at a pressure of mm.of mercury.

The ester product from this reaction was characterized by a hydroxylvalue of 567:5 and a total fatty acid content of 166.1%. Theanalytically determined hydroxyl value of 567.5 compares favorably witha calculated value of 570 indicating the substantial absence of anhydrogroups in the product.

Example V The process of Example III was repeated except that 18 partsof mannitol was used in place of sorbitol as the hexitol reactant.

The ester product from this reaction had a hydroxyl value of 484.4 (thiscompares with a calculated hydroxyl value for this product of 482) and atotal fatty acid content of 70.6%.

Example Vl The process of Example VI was repeated except that thereaction was conducted at a temperature of 100 C. and under a pressureof 30 mm. of mercury.

Upon analysis, the ester product Iwas found to have a hydroxyl value of475.3 (476 is the calculated hydroxyl value of the product) and a totalfatty acid content of 70.8%. l

Example VIII 3-6 parts of mannitol, 87.5 parts of a mixture of 80%soybean oil and 20% cottonseed oil hydrogenated to an iodine value ofabout 76, and' about 360 parts of dimethylacetamide were introduced intoa reaction vessel provided with mechanical stirring means. This mixturewas heated to a temperature of '100 C. and then 1% of sodium methoxidecatalyst by weight of the fatty material was added to the heatedmixture. (The sodium methoxide was added as a 10% suspension in xylene.)The resulting mixture, while being agitated, was allowed to react forone hour under atmospheric pressure. The catalyst was then inactivatedby the addition to the reacting mixture of a 50% aqueous solution ofacetic acid. The resulting mixture was then treated in accordance withthe procedures set forth in Example I to isolate the mannitol-fattyester.

The ester product was found to have a hydroxyl value of 342.3 and atotal fatty acid content of 77.39%.

In the foregoing example diethylacetamide, monobutyl acetamide,monoethyl acetamide, monomethyl butyramidc, monomethylpropionamid'e anddimethyl butyramide can be substituted for dimethyl acetamide as thesolvent reaction medium with the production of a hexitol-fatty ester ofsubstantially the same degree of esterification and of 564.4 comparesfavorably with the calculated hydroxyl 75 freedom from anhydroconfigurations.

, dirnethylsulfoxi'de was used as the reaction medium. v v .The esterproductv of this reaction was found to have a hydroxyl value of 329.2and a total fatty acid content f 78.67%

Example X I The process of Example vVIII was repeated except thatsorbitol was utilized. inplace of mannitol as the hexitol reactant.

The ester product from this reaction was found to have a hydroxyl. valueof 378.8 and a total fatty acid content of 77.23%. Y

Example XI The process of Example X was repeated utilizingdimethylsulfoxide as the solvent reaction medium.

The ester product of this reaction was found to have a hydroxyl value of332.9 and a total fatty acid content of 78.74%.

In the foregoing examples the hydroxyl values (H.V.) and percent totalfatty acids (T.F.A.) of the products were determined analytically inaccordance with Official Method. Cd 4410 and Tenative Method GBL-53respectivelyl of the `Official land Tenative Methods of the American OilChemists Society.

Wherever set forth herein the calculated hydroxyl values of the sorbitoland mannitol fatty esters were obtained using the following equations:

(a) For -sorbitol and mannitol palmitates- K H.v.=1s51-- V T.F.A.(observed) where 1851.=H.V. of sorbitol or mannitol and A95.4=T.F.A. ofsorbitol or mannitol hexapalmitate ester (b) F or ester products fromthe reaction of sorbitol or mannitol with the soybean oil-cottonseed oiladmixture- -WS-XTA. (observed) where 1851.=I1V. of sorbitol or mannitoly'and Compound ILV. T. 131A.

Sorbitol Monopalmitate 668 61. Sorbltol Dlpalmitate 342 77. 8 SorbitolHexapalmitate. 0 95. 4 Sorbitan Monopalm'itate 429 63. 7 SorbitanDipalmitate- 175 80. 0 Sorbtan Tetrapalmltate 0 91.7 Sorbltide`Monopalrntate 145 66. 7 Sorbitide Dpalmitate 0 82. 3

The hydroxyl values of the products of each of the spec examples hereinhave been indicated in FIGURE I and have been numbered to conform withthe respective examples.

In. FIGURE'I the curve delineated by the calculated values for theproducts obtained from the interesteriiica-V tion offsorbitol ormannitol with the soybean oilcottonseed toill mixture'ha-s not. beenindicated. Based upon calculated points represented by an II.V. of 629and T.F.A. of 63.2 -for the monoester of sorbitol andthe soy beanoil-cottonseed oil mixture and ian H.V. of 0 and a T.F.A. of 95.75 forthe hexe-ester of sorbitol and the oilf mixture :and'being astraight-line relationship, this curve was found lto s-o closelyapproximate the sorbitol palmitate curve of FIGURE I that the lattercurve was util-ized as a comparison reference for the products ofExamples VIII, IX, X and XI as Well' as those of Examples I to VII.

Elie excellent agreement between the `analytically ob-` tained values ofthe products of the examples and the' curve representing the calculatedvalues for -anhydro-free sorbitol-fatty esters is readily apparent.

`It is t-o be understood that in the foregoing examplesthe sorbitolV andmannitol may =be replaced with other straigh'tf chain hexitols'hereinbefore mentioned' with comparable results. Similarly, other fattyesters of the character indicated Ihereinbefore may be substituted forthe fatty ester groups, in the presence of .an interestericationcatalyst;

at a temperature in the range from about 50 to about 150 C., and in thepresence of -a solvent selected from ther group consisting of (l)sul-foxides of the general formula? S=O R/ where R `and R' are alkylgroups having from 1 to 3r carbon atoms, and (2) :amides `of the generalformula' Rl R-CON/ n RII where Rand R tare selected from the groupconsisting of` hydrogen and an alkyl group having from 1 to 4 carbonlatoms, and R" isv an alkyl group having from 1 to 4 carbon atoms, thetotal number of carbon atoms in R, R' and R being not `greater rthan 7,the said :aliphatic primary monohydroxy alcohols containing from 1 toabout 8 carbon atoms in the presence of a sulfoxide solvent and from lto about 16 carbo-n atoms in the presence of `an amide solvent, the saidsolvent being present in an amount a-t least sufficient to dissolve thestraight-chain hexitol.

2. The process of claim 1 wherein the straight-chain hexitol issorbitol.

3. The process of claim 1 wherein the straight-chain hex-itol ismannitol.

4. The process of claim l wherein the straight-chain hexit'ol isdulcitol.

5. The process of claim 1 wherein the solvent is dimethylacetamide.

6. The process of claim 1 wherein the solvent is di methylsulfoxide.

7. A process for preparing fatty esters of straight-chain hexitols,which esters are substantially free from anhydro groups, comprisingreacting a straight-cham hexitol with a fatty acid ester selected fromthe group consisting of fatty 4acid esters of aliphatic primarymonohydroxy alcohols and fatty acid esters of polyhydroxy alcohols, all'of which alcohols have not more ,than three carbon `atoms in thepresence of an interesterication catalyst, at a temperature in the rangefrom about to about 150 C., and -in the presence of a solvent selectedfrom the group consisting of: (1) sulfoxides of the general formulawhere R and R are yalkyl groups having from 1 to 3 carbon atoms; and (2)amides of the general formula R, R4CON/ hexitol is sorbitol.

9. The process of claim 7 wherein the straight-chain heXitol ismannitol.

10. The process of claim 7 wherein the solvent is dimethylacetamide.

ll. The process of claim 7 wherein the solvent is dimethylsulfoxide.

12. A process for preparing fatty esters of straightchain heXitols,which esters are substantially free from anhydro groups, comprisingreacting a straight-chain hexitol with a fatty acid ester of glycerol inthe presence of from about 0.1% to about 2% of an interestericationcatalyst by weight of the glycerol ester at a temperature in the rangefrom about 90 to 150 C. and in a reaction medium comprising essentiallya solvent selected from the group consisting of (l) sulfoxides of thegeneral formula where R and R are alkyl groups having from l to 3 carbonatoms; and (2) amides of the general formula R-CON/ RII where R and Rare selected from the group consisting of hydrogen and an alkyl grouphaving from 1 to 4 carbon atoms, and R" is an alkyl group having from 1to 4 carbon atoms, the total number of carbon atoms in R, R and R beingnot greater than 7.

13. The process of claim 12 wherein the fatty acid ester is atriglyceride.

14. The process of claim 13 wherein the straightchain heXitol issorbitol.

15. The process of claim 13 wherein the straightchain hexitol ismannitol.

16. The process for preparing fatty esters of straightchain heXitols,which esters are substantially free from anhydro groups, which comprisesreacting a straight-chain hexitol with a fatty acid ester of methanol ina reaction medium comprising essentially a solvent selected from 10 thegroup consisting of (l) sulfoxides of the general formula where R and R'are alkyl groups having from 1 to 3 carbon atoms; and (2) amides of thegeneral formula /R' R-CON RII where R and R' are selected from the groupconsisting of hydrogen and an alkyl group having from 1 to 4 carbonatoms, and R" is an alkyl group having from 1 to 4 carbon atoms, thetotal number of carbon atoms in R, R and R being not greater than 7, inthe presence of from about 0.1 to `about 2% of an interestericationcatalyst, by weight of the methyl ester, at a temperature in the rangefrom about to 150 C. and at a suflciently low pressure that the methanolliberated during the reaction is continuously distilled from thereaction mix, whereby the reaction proceeds to substantial completeness.

17. The process for preparing fatty esters of straightchain hexitols,which esters are substantially free from anhydro groups, comprisingreacting a straight-chain heXitol and a fatty triglyceride, in thepresence of an interesterilication catalyst, `at -a temperature of aboutC., in a reaction medium comprising essentially dimethylacetamide,inactivating the catalyst by acidulation, distilling substantially allof the dimethylacetamide from the reaction mixture, taking up theresidue in a solvent and water-washing the resultant solution, removingthe solvent by evaporation under vacuum and purifying the ester product.

18. The process for preparing fatty esters of straightchain hexitols,which esters are substantially free from anhydro groups, comprisingreacting a straight-chain hexitol and a fatty triglyceride, in thepresence of an in- References Cited in the le of this patent UNITEDSTATES PATENTS 2,223,558 Epstein Dec. 3, 1940 2,357,077 Brown Aug. 29,1944 2,357,078 Brown Aug. 29, 1944 2,812,324 Huber et al. Nov. 5, 19572,831,854 Tucker et al. Apr. 22, 1958 2,893,990 Hass et al. July 7, 1959

1. A PROCESS FOR PREPARING FATTY ESTERS OF STRAIGHT CHAIN HEXITOLS,WHICH ESTERS ARE SUBSTANTIALLY FREE FROM ANHYDRO GROUPS, COMPRISINGREACTING A STRAIGHT-CHAIN HEXITOL WITH A FATTY ACID ESTER SELECTED FROMTHE GROUP CONSISTING OF FATTY ACID ESTERS OF ALIPHATIC PRIMARYMONOHYDROXY ALCOHOLS AND COMPLETELY AND INCOMPLETELY ESTERIFIED FATTYACID ESTERS OF POLYHYDRIC ALCOHOLS HAVING FROM 2 TO 6 HYDROXYL GROUPS,IN THE PRESENCE OF AN INTERESTERIFICATION CATALYST, AT A TEMPERATURE INTHE RANGE FROM ABOUT 50* TO ABOUT 150* C., AND IN THE PRESENCE OF ASOLVENT SELECTED FROM THE GROUP CONSISTING OF (1) SULFOXIDES OF THEGENERAL FORMULA